A YSPH professor discusses the rapid spread of the mosquito-borne disease.
Professor Durland Fish of the Yale School of Public Health has researched a variety of vector-borne diseases associated with ticks and mosquitoes. His work involves ecology, evolution and the affects of climate change on the transmission and range of a host of diseases, including babesiosis, Lyme disease, malaria, dengue fever and, more recently, chikungunya. Spread by mosquitoes, chikungunya first appeared in the Americas late last year and has since spread rapidly to other areas of the hemisphere. There are now confirmed cases in the continental United States. Fish traveled to the island of Dominica earlier this year to work with local health officials as they dealt with a large influx of new chikungunya infections and tried to coordinate a public health response to prevent further spread of what has become an epidemic.
Q: Cases of chikungunya have now been confirmed in Florida. Is the disease likely to spread farther into the United States?
DF: I think it is likely to spread, but not necessarily from Florida. Travelers from areas where chikungunya is epidemic arrive everyday to many cities in the United States where mosquitoes could get infected and cause local transmission.
Q: Could it reach as far north as Connecticut?
DF: It is possible, but less likely because we are at the northern range where mosquitoes that transmit chikungunya can survive. But that could change with global warming.
Q: How serious a public health threat is this disease?
DF: This depends upon the region. In Latin America and the Caribbean, where another mosquito-borne disease called dengue fever occurs, the added disease burden of chikungunya could decrease the overall effectiveness of health services, at least temporarily until the epidemic burns itself out. In the United States, where a large epidemic is not expected, there could be continuous low level of transmission in certain areas that might affect tourism.
Q: Chikungunya is spread by a species of mosquito known as Aedes aegypti. Is this species common and widespread in the United States?
DF: There are two mosquito species that can transmit chikungunya virus, the yellow fever mosquito Aedes aegypti ,which is tropical and common in the southern states and the Asian tiger mosquito Aedes albopictus, which is both tropical and temperate and has a much larger range. The abundance of each varies locally and seasonally, but both are most common in urban areas.
Q: How has the public health response been since this disease first appeared in the Americas last year?
DF: Obviously, rather ineffective since there are probably over a million cases since the virus was first introduced on the island of St. Martin in the Caribbean sometime last December.
Q: Did this play a role in its rapid spread?
DF: Yes, there seems to have been only a single introduction from Asia that started this epidemic. It gives you an idea of how unprepared we are for these kinds of epidemics and how inept we are at controlling them. Fortunately, chikungunya has a low mortality rate (0.1 percent), unlike yellow fever (10 percent to 20 percent).
Q: Could a more forceful, concerted response have stopped or limited its spread?
DF: Probably not, but I believe it could have slowed the spread which would have given more time for preparation and caused less disruption of health case systems. There is little evidence that dengue fever epidemics can be prevented through traditional mosquito control activities and chikungunya is probably even harder to prevent.
Q: Describe the work on chikungunya that you did on the island of Dominica.
DF: We tried to contain the virus by isolating febrile patients from mosquitoes with bed nets so they could not infect mosquitoes, and also treating houses with insecticide to kill any mosquitoes that the patient may have already infected. If you can prevent mosquitoes from becoming infected, you can prevent people from becoming infected since people are the source of infection and they move the virus around. There were 30 cases when I arrived and 60 more next week. By then, 20 new cases were coming in each day and it was impossible to maintain a containment operation. The battle was soon lost and it was a sobering experience for me. Now, we are working with public health officials in Dominica to try to understand what happened as this will be repeated over and over as the epidemic moves through the Caribbean and onto the mainland.